1. Field of the Invention
The present invention relates to an apparatus and method of driving a liquid crystal display (LCD) device, which has a simplified structure by decreasing the number of signal transmission lines providing signals to a shift register.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) device displays images under the control of light transmittance in liquid crystal. The LCD device is comprised of an LCD panel which includes a plurality of pixel regions arranged in a matrix configuration; and a driving circuit which drives the LCD panel.
The LCD panel includes a plurality of gate and data lines being orthogonal to each other, and a plurality of pixel regions defined by the gate and data lines being orthogonal to each other. To apply an electric field to each pixel region, there are pixel electrodes and a common electrode. Each of the pixel electrodes is electrically connected to a thin film transistor (TFT) which functions as a switching element. The thin film transistor (TFT) is turned-on by a scan pulse of the gate line, whereby the pixel electrode is charged with a data signal of the data line.
The driving circuit includes a gate driver to drive the gate lines; a data driver to drive the data lines; a timing controller to supply control signals to the gate and data drivers; and a power source to supply power source signals to the LCD panel, the gate and data drivers, and the timing controller.
The gate driver includes a shift register to output scan pulses in sequence. The shift register is comprised of a plurality of stages cascaded with one another, wherein the plurality of stages sequentially output the scan pulses to scan the gate lines of LCD panel. A first stage among the plurality of stages is supplied with a start pulse from the timing controller and the others stages are supplied with a start pulse, an output signal outputted from the preceding stage. And the plurality of stages are supplied with at least one of a plurality of clock pulses having the sequential phase differences. The plurality of stages output the scan pulses to the gate lines of LCD panel in sequence. Accordingly, the gate driver needs a plurality of signal lines to supply the start pulse and the plurality of clock pulses.
However, if the shift register is formed in and is integrated with a thin film transistor (TFT) array substrate of the LCD panel, the TFT array substrate includes the plurality of signal lines to supply the start pulse and the plurality of clock pulses from the timing controller to the shift register.
A start pulse line is formed on the TFT array substrate, wherein the start pulse line is formed of the same metal material as the gate or data line. Also, the start pulse line is connected to the first stage and the dummy stage among the plurality of stages included in the shift register. Thus, the shift register is increased in size so that the shift register occupies the large space of TFT array substrate.
If providing at least one dummy stage to reset the last stage among the plurality of stages which generate the plurality of scan pulses in sequence, the size of shift register is increased more.